Press for sheathing cables



2 Sheets-Sheet 1 April 5, 1960 w. HAENDELER mass FOR SHEATHING CABLESFiled Feb. 28. 1955 -=HIIIII||1 IHIH -==!IJIH|H /NVNTOP fl HQ: 812, aleLen 6 2 N m 1 m 3 S a 2 m I April 5, 1950 .'HAENDELER P S FOR SHEATHINGCABLES Filed Feb. 28. 1955 lNVL-NTO/P NE a 812658 la (g TTYJ 2,931,496PRESS non SHEATHING CABLES Walter Haendeler, Dusseldorf, Germany,assignor to Schloema'nn Aktiengesell'schaft, Dusseldorf, GermanyApplication February 28, 1955, Serial No. 491,123

Claims priority, application Germany March 18, 1954 2 Claims. c1. 201-47 than the external diameter of that part of the cable which is not yetsheathed. The cable running into the device, and not yet sheathed,passes therefore with some play through the point of the mandrel so thatit does not have to be directly in contact with the hot point of themandrel. Contact between the cable and the hot point of the mandrel. isparticularly dangerous duringthose periods when the press is stoppedbecause the cable in sulation is then destroyed by the eifect of theheat. It is the purpose of the present invention to prevent withcertainty any contact between the cable and the mandrel and theinvention employs for this purpose the protective tube mentioned above.The invention is based on a known type of press for sheathing cableswith aluminium, where a cooled protective tube surrounding the cable isintroduced in the mandrel of the press, the front end of the said tubebeing concentric with the mandrel, but at some distance from the saidmandrel. It is necessary to maintain this distance while the cable isbeing sheathed with aluminium, because the mandrel of the press must bekept hot enough to avoid the cooling of the aluminium within the area ofthe mandrel during the stopping intervals of the press to a temperaturewhich would render the continuation of the pressing process impossible.But this temperature of the point of the mandrel represents a danger forthe insulation of the cable.

According to this invention the front end of the protective tube has abore which is smaller than the bore of the point of the mandrel. Thepart of the cable which is not yet sheathed is passed through the saidtube in such a way that it is never directly in contact with or even inthe immediate neighbourhood of the hot point of the mandrel.

It is known that in lead presses the protective tube is tapered at thefront and the conical surface is placed against the hollow conicalinternal surface of the mandrel, so that the mandrel is cooled by thecooled protective tube. In this case the protective tube is under theaction of a force, for instance the pressure of a spring, which pushesthe tube into the mandrel. Thus the front end of the protective tube isforced to make contact over a wide internal surface with the mandrel,and also the concentric position of the protective tube with respect tothe mandrel is ensured. Since also in the case of the press of thepresent invention it is aimed to place the protective tube in aconcentric position, while on the other hand the cooling'of the mandrelby the protective tube is to be prevented, the surface of con- StatesPatent-O v the protective tube would not then be required.

2,931,496 Patented Apr. 5, 1960 tact between the mandrel andtheprotective tube is kept as small as possible according to theinvention.- This iseifected as follows: When the bore of the mandrel hasthe shape of a hollow cone, or the protective tube is extcrnallyconical, one of these two conical surfaces is provided with smallcontact surfaces, for instance lugs or other stops, against which theother conical surface bears.

In order that the invention may be clearly'understood and readilycarried into eifect, thesame will nowbe described more fully withreference to the accompanying drawings, in which:

Figure '1 is the general arrangement of a mandrel with a protective tubeaccording to the invention; and

FigureZ shows on a larger scale the position of the front end of the"tube with respect to the point of the mandrel.

The mandrel 1. is inserted into the mandrel holder 2, which in its turnis held by a bush 3 screwed into the press body 4. The front end 5 ofthe protective tube 7 is pushed into the mandrel 1. The protective tubeis designed as a cooling pipe. The cooling water runs into the pipe atits rear end at 8 and leaves the pipe at 9, in a known manner. The cablewhich is to round the cable 15. As shown in the drawing, the here In ofthe point of the mandrel 1 is a little larger than the bore 5a of thefront end 5 of the protective tube 7, so that the cable, when it makescontact with the front end of the tube, just avoids touching theinternalsun face of the point of the mandrel, which may be heated to ahigh temperature due, for instance, to the high temperature of thealuminium that is being extruded. The bore 1a of the point of themandrel has an internally frusto-conical'surface at 1b and may have forinstance, a vertex angle of 30, so that the generatrix of thefrustoconical surface 1b in the section makes an angle of 15 with thecable axis. The front end 5 of the tube 7 is also tapered and is withits four stops 16 concentric with the hollow frusto-conical surface 1b.The springs 17 apply a pressure at the rear end of the protective tube 7and tend to push it constantly forward, as shown in Figure 1. Theaccurate concentric position of the tube in the mandrel canalso beachieved by ensuring that the tapered end of the protective tube makescontact with a ring of stops at about the position 1c, which projectinwards from the internal conical bore of the mandrel. Theaforementioned stops 16 projecting outwards from If preferred, the ringof stops 10 may be replaced by a continuous internal annular shoulder onthe mandrel. The contact surfaces of the stops 10 or of the shouldersubstituted for them would have a conical curvature, so as to bearsmoothly upon the conical surface of the protective tube, and it wouldnot then be essential for the internal surface of the mandrel itself tobe conical.

The vertex angle of the cone of which the contact surfaces form partsmust be greater than the angle of friction between the materials ofwhich the mandrel and the protective tube are composed. By the angle offriction is meant that angle the tangent of which is equal to thecoefiicient of friction. In the case of a body resting on an inclinedplane, it is the maximum angle of inclination of the plane at which thebody could rest without slipping down. If the angle between the surfacesof contact on opposite sides of the axis, or in other words the vertexangle of which the surfac s of As shown contact form parts, is. greaterthan the angle of friction, any increased inward radial pressure betweenthe surfaces, occasioned for example by the mandrel contracting owing toa fall of temperature, would push back the protective tube 7 against thethrust of the springs 17, thus maintaining the correct co-axialrelationship between the protective tube and the mandrel.

The exact angle of friction between the internally frusto-conicalsurface 1b of the mandrel 1 and the contact surfaces of the stops 16, orbetween the conical surface of the front end 5 of the protective tube 7and the stops 1c or the shoulder substituted for them, would of coursedepend upon the materials employed, the surface finish and thetemperature, but its possible range of values would be known or could beascertained for any particular case, and in designing the press theangle in question must be made greater than the maximum value of theangle of friction. The above-mentioned angle of 30 degrees betweencontact surfaces on opposite sides of the axis, or in other words ofdegrees on each side of the axis, is believed to be quite a safe valueto adopt,

I claim:

1. A press for sheathinginsulated electric cables with aluminum, theextrusion temperature of which would be dangerous to the insulation ofthe cable, comprising a hollow mandrel internally tapered toward itsfront end, an axially movable protective tube within and spaced rom theinternal wall of the mandrel and through which the cable tobc sheathedis fed to the front end of the mandrel of the press, means for coolingthe protective tube, the internal diameter of the front end of the protective tube being smaller than the bore of the front end of themandrel, and an annular array of stops having small areas of contactextending between the internal tapered wall of the mandrel and theexternal wall of the tube adjacent its front end for maintaining thefront end of the protective tube coaxial with and rearwardly ,of thefront end of the mandrel with a suitable gap between the tube and. themandrel, whereby said small areas of contact minimize heat transferbetween said mandrel and said tube.

2. A press for sheathing insulated electric cables as claimed in claim1, the front end of the protectivetube being externally frusto-conical,and the press further comprising resilient means urging the tube towardthe front end of the mandrel.

References Cited in the file of this patent OTHER REFERENCES AppliedMechanics, by Alfred P. Poorman, 3rd. ed., McGraw-Hill Book Co., Inc.,copyright 1930, pp. 106-108. 1

Physics, by E. Hausmann and E. P. Slack, 3rd. ed., D. Van Nostrand Co.,Inc., copyright 1948, 3rd. par. p. 86.

